Enzymatic Protein Hydrolysates Research Articles

Cricket (Acheta domesticus) protein hydrolysates’ impact on the physicochemical, structural and sensory properties of tortillas and tortilla chips

Consumer interest towards consumption of more sustainable protein sources has led way towards the adoption of insect protein for human food applications. Research shows that insect proteins utilised as food ingredients are more promising to be accepted by Westerners. In this study, cricket protein hydrolysates (CPH) were produced using Alcalase (AL) and Flavourzyme (FL) proteases. The physicochemical and structural properties, as well as the sensory acceptability of corn tortillas formulated with 20% (w/w) CPH were evaluated. CPH-tortillas contained all essential amino acids, including 40% of the daily lysine requirement. In raw corn masa (dough), AL-CPH increased the elastic modulus (G’), indicating cross-linking between polymers, while FL-CPH decreased G’. Tortillas formulated with AL-CPH resulted in matrices with low hardness and extensibility values, while FL-CPH tortillas developed a strong and flexible structure, indicating differences in intermolecular interactions between the AL- and FL-CPH and the tortilla matrix in the cooked tortillas compared to the raw masa. Sensory evaluation results showed acceptability (scores>6.0) towards tortillas chips formulated with 20% CPH. Enzymatic hydrolysis of cricket protein can create peptides with functional characteristics and sensory acceptability for their use as ingredients in food formulation.

Dealing with soy sauce precipitation at submicron-/nano-scale: An industrially feasible approach involving enzymolysis with protease and alkaline conditions

This study proposes an industrially feasible approach to handle the heating-induced soy sauce precipitates (SSPs) during soy sauce production. Protein (32.59%; containing a large amount of hydrophobic amino acid) and sugar (26.86%) were found to be the main composition of SSPs, and high content of mineral elements were also discovered in SSPs. A pH adjustment to 8–12 along with an enzymolysis step with alkaline protease seemed beneficial for this purpose while offering opportunities to manipulate the soy sauce quality. The pH adjustment decreased SSPs particle size from micron-scale to submicron- or nano-scale, and improved significantly the efficiency of SSPs protein enzymatic hydrolysis and protein recovery (up to 80%). The enzymolysis with alkaline protease enabled the generation of pyrazines while affecting the contents of phenols, alcohols, furans, pyrroles and sulfur-containing compounds. Interactions occurred between amino acids and sugars, among volatiles, and between volatiles (like aldehydes) and other monomers under such alkaline conditions. This study presents an efficient approach that is of practical significance to dealing with SSPs in soy sauce production and reuse of SSPs.

Antioxidant peptides from Mytilus Coruscus on H2O2-induced human umbilical vein endothelial cell stress

The enzymatic protein hydrolysates of Mytilus coruscus (MCPH) were prepared with 5 proteases. The low molecular weight (MW) peptide fractions (<1 kDa, MCPH-T1) of trypsin hydrolysates were obtained using ultrafiltration. MCPH-T1 showed the most competitive DPPH•, ABTS+•, OH•, and O2−• scavenging activities compared to other enzymatic hydrolysates or high MW fractions. Compared to glutathione, MCPH-T1 showed better ferric ion-reducing power and inhibited lipid peroxidation of linoleic acid. In H2O2-induced oxidative injured of human umbilical vein endothelial cells (HUVEC), MCPH-T1 pre-treatment improved cell viability and ameliorated the morphological damage through attenuating the accumulation of reactive oxygen species (ROS) and malondialdehyde (MDA) production and restored the cellular antioxidant capacities. In addition, MCPH-T1 showed a cytoprotective effect on dysfunctional cell by regulating the expressions of apoptotic and NF-κB proteins and restored the Nrf2-driven antioxidant defense mechanism. These results indicated that MCPH-T1 may be potential food ingredients for managing oxidative stress-related endothelial dysfunction or related cardiovascular diseases.

Comparative study of composition, antioxidant and antimicrobial activity of two adult edible insects from Tenebrionidae family

In the case of Tenebrionidae family insects, studies focus on larval stage, leaving a lack of information regarding other stages. Therefore, this study was performed in order to understand the differences between the nutritional composition and the bioactivity of two species of this family in their adult stage, fed with a specific diet. Adult beetles of both species were defatted, lyophilized and protein extracted with buffer. Proximal and phytochemical analysis of the extracts of each insect were performed, along with protein extract and hydrolysis analysis by Tris-Tricine and Tris Glycine SDS PAGE. This analysis showed that T. molitor contained more protein and fat than U. dermestoides but contained less crude fiber. The protein extraction was made with PBS, where 130 and 45 kDa bands showed predominant for U. dermestoides, and less protein was present for T. molitor. Antioxidant and antimicrobial activities of the enzymatic protein hydrolysates and protein crude extracts were determined. Presence of protein associated with the antioxidant activity were found in both insects. Nonetheless U. dermestoides had a higher antioxidant activity with the protein extract in contrast with the higher antioxidant activity shown by U. dermestoides once the extracts were digested. After proteolysis, protein extracts showed an increasing antioxidant activity, plus, the ability to inhibit microbial growth of Proteus, Shigella and Bacillus. Insect protein hydrolysates with protease open the possibility for the use of these beetles as new sources of encrypted peptides for microbiological control once characterized.

Substantial Improvement of Tryptic and Chymotryptic Hydrolysis of β-Lactoglobulin Pretreated with High Voltage Electrical Treatments

β-lactoglobulin (β-lg) is an important source of biologically and functionally active peptides that are of particular interest in agri-food, nutraceutical, and pharmaceutical industries. Enzymatic hydrolysis of proteins remains the most common mode of peptide production. However, efficient hydrolysis of proteins and particularly β-lg is difficult to perform due to their compact globular structure. Thus, the current study deals with green high-voltage electric treatments (HVET): pulsed electric fields and electric arc to pretreat β-lg and improve its proteolysis by trypsin and chymotrypsin. The results demonstrate substantial improvement of hydrolysis performance after the pretreatment of β-lg with HVET compared to the non-pretreated and preheated β-lg. Moreover, HVET led to the peptide release from β-lg even before the addition of proteases. Furthermore, pioneer studies of proteolysis kinetics and structural changes of β-lg molecules subjected to HVET allowed a better understanding of the mechanisms underlying hydrolysis improvement.

Effects of fermentation periods on antioxidant and angiotensin I-converting enzyme inhibitory activities of peptides from fish sauce by-products

Manufacturing of fish sauce results in a large number of underutilized by-products. The fish sauce by-products (FSBs) contain peptides derived from enzymatic hydrolysis of the fish proteins by proteases from their gastrointestinal tract and halophilic microorganisms. Commercial fish sauce can be divided into different grades based on their fermentation period. The 1st, 2nd and 3rd grade FSBs are solid wastes produced after the 1st, 2nd and 3rd grade fish sauce fermentation. This work aims to evaluate the effect of fermentation periods on antioxidant and angiotensin I-converting enzyme (ACE) inhibitory activities of the FSBs. Based on bioassays against different mechanisms, the 1st grade FSB possessed stronger DPPH and hydroxyl radical scavenging activities and reducing ability than the 2nd and 3rd grades. The top two grades of FSB showed higher % ACE inhibition than the 3rd grade FSB. All FSBs had equally strong H2O2 quenching and iron chelating abilities. It was observed that FSB fractions with smaller molecular weight and higher hydrophobicity possessed higher antioxidant and anti-ACE activities. This work demonstrated that the manufacturing fermentation time affected activities of FSB peptides. Understanding of composition and bioactivities of the FSBs may lead to the development of value-added functional products from these manufacturing wastes.

Thermoase-hydrolysed pigeon pea protein and its membrane fractions possess in vitro bioactive properties (antioxidative, antihypertensive, and antidiabetic).

Enzymatic hydrolysis can liberate bioactive peptides from protein materials, thus, pigeon pea was hydrolysed using thermoase. Crude hydrolysate (PPHT) was subjected to ultrafiltration using different molecular weight cutoffs to collect <1, 1-3, 3-5, 5-10, and >10kDa peptide fractions. Fractions were analysed for in vitro antioxidative, antihypertensive, and antidiabetic properties. The peptide fractions had stronger DPPH• scavenging and renin inhibition when compared to PPHT. In contrast, ACE inhibition was stronger for the PPHT and <1kDa peptide fraction while activity decreased as peptide size increased. The <1kDa peptide also showed significantly stronger ferric reducing antioxidant power, OH• scavenging and inhibition of linoleic acid oxidation when compared to PPHT. α-amylase and α-glucosidase were inhibited by all the peptide fractions, though the 3-5 and >10kDa had higher values. We conclude that the PPHT and peptide fractions could serve as potential ingredients to formulate antihypertensive and antidiabetic functional foods and nutraceuticals. PRACTICAL APPLICATIONS: Oxidative stress promotes the generation of free radicals, which have a significant impact in the pathogenesis of human chronic diseases such as cardiovascular impairment, cancer, and diabetes. Peptides generated from enzymatic hydrolysis of proteins have been identified to impart beneficial health effects. In this work, we showed that a thermoase digest of pigeon pea protein as well as the fractionated peptides had strong antioxidant properties in addition to exhibiting inhibitory activities against renin and angiotensin converting enzyme, the main therapeutic targets for antihypertensive agents. The peptide products also inhibited α-amylase and α-glucosidase activities, providing potential ingredients that can be used to formulate antidiabetic functional foods.

Scaling up the Enzymatic Hydrolysis of Bovine Plasma Protein to Produce an Antioxidant from a Biological Source.

In modern society, there is a tendency to consume products with natural origins and minimum chemical additives. This has encouraged the replacement of synthetic antioxidants for the ones obtained from natural sources, such as the antioxidants acquired from enzymatic protein hydrolysates. In this study, the process of enzymatic hydrolysis of proteins from bovine plasma, which produces hydrolysates with an Antioxidant Capacity (AC), was scaled up from 1 to 5 L. An experimental design was developed in 1 L to evaluate the effect of the Substrate concentration (So) on the time needed to reach a Degree of Hydrolysis (DH) of 20% as well as the AC. The best conditions in the 1 L reactor controlled by a Titrando 842 were transferred to 5L in a BioFlo310 reactor. These conditions were achieved at a ratio of 80g/L of the substrate and 0.89 AU of Alcalase 2.4L/g of the substrate in order to obtain a level of 16.36 ± 0.21min of the 20% of DH and antioxidant capacity of 58.98 ± 1.80%. The results showed that DH depends significantly on So, while the antioxidant capacity only depends on the DH. Additionally, the dimensional analysis using Re as a scaling criterion allowed us to obtain the same results in the model (1 L) and the prototype (5 L).

Dromedary Milk Protein Hydrolysates Show Enhanced Antioxidant and Functional Properties.

SUMMARYResearch backgroundMilk protein hydrolysates have received particular attention due to their health-promoting effects. Dromedary milk differs from the milk of other dairy animals in the composition and structure of its protein components, which give it unique properties. The bioactivity and functionality of whole dromedary milk proteins and their enzymatic hydrolysates have not received much attention, hence this study aims to investigate the effect of enzymatic hydrolysis of dromedary milk proteins on their antioxidant activities and functional properties.Experimental approachDromedary milk proteins were treated using four proteolytic enzymes (pepsin, trypsin, α-chymotrypsin and papain) and two mixtures of enzymes (pancreatin and pronase). The degree of hydrolysis was measured to verify the hydrolysis of the proteins. The sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration chromatography served to determine the molecular mass distribution of the hydrolysates while reversed phase-high performance liquid chromatography (RP-HPLC) was conducted to explore their hydrophobicity. The antioxidant activities were evaluated using various in vitro tests, including 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical scavenging capacities, iron(III) reducing ability and chelating activity. Besides, functional properties such as solubility, foaming and emulsification were assessed.Results and conclusionsDromedary milk protein hydrolysates exhibited different degrees of hydrolysis ranging from 17.69 to 41.86%. Apart from that, the hydrolysates showed different electrophoretic patterns, molecular mass distribution and RP-HPLC profiles demonstrating the heterogeneity of the resulting peptides in terms of molecular mass and polarity. The hydrolysates displayed significantly higher antioxidant capacities than the undigested proteins at all the tested concentrations. Iron(II) chelating activity was the most improved assay after proteolysis and the hydrolysate generated with pancreatin had the highest chelating power. Dromedary milk protein hydrolysates possessed good solubility (>89%). Further, foaming and emulsifying properties of dromedary milk proteins were enhanced after their proteolysis. These interfacial properties were influenced by the enzymes employed during proteolysis.Novelty and scientific contributionEnzymatic hydrolysis of dromedary milk proteins is an effective tool to obtain protein hydrolysates with great antioxidant and functional properties. These results suggest that dromedary milk protein hydrolysates could be used as a natural source of antioxidant peptides to formulate functional foods and nutraceuticals.

Enzymatic fish protein hydrolysates in finfish aquaculture: a review

AbstractIn intensive farming systems, fish are held at high densities, which may increase stress, leading to susceptibility to diseases that result in economic losses. Therefore, effective feeding practices incorporating health‐promoting compounds such as proteins, hydrolysates and bioactive peptides that can stimulate the defence mechanisms of fish and achieve better growth are some of the priorities for sustainable aquaculture development. Globally, the fish processing industries generate and discard a large volume of waste every year, estimated at up to 60% of the harvested biomass. This waste can be converted to value‐added products such as fish protein hydrolysate (FPH) with the addition of various proteolytic enzymes. FPH from fish processing waste including skin, heads, muscle, viscera, liver and bones is a good source of protein, amino acids, peptides and antioxidants and has been found to possess desirable functional and bioactive peptides. A moderate inclusion of FPH in aquafeeds has the potential to improve growth, feed utilization, immune functions and disease resistance of fish. Production of FPH, targeted to more precise molecular weight ranges, has superior functionalities that are in high demand. With interest in FPH as an aquafeed supplement, this review aimed to summarize the source, production processes and functional properties of FPH and the reported impact of FPH in aquafeed supplement on fish growth, survival, feed utilization, immune response and disease resistance. Possible limitations of using FPH and future research potential as an opportunity for the use of processing fish waste are also discussed.

Antidiabetic Food-Derived Peptides for Functional Feeding: Production, Functionality and In Vivo Evidences.

Bioactive peptides released from the enzymatic hydrolysis of food proteins are currently a trending topic in the scientific community. Their potential as antidiabetic agents, by regulating the glycemic index, and thus to be employed in food formulation, is one of the most important functions of these peptides. In this review, we aimed to summarize the whole process that must be considered when talking about including these molecules as a bioactive ingredient. In this regard, at first, the production, purification and identification of bioactive peptides is summed up. The detailed metabolic pathways described included carbohydrate hydrolases (glucosidase and amylase) and dipeptidyl-peptidase IV inhibition, due to their importance in the food-derived peptides research field. Then, their characterization, concerning bioavailability in vitro and in situ, stability and functionality in food matrices, and ultimately, the in vivo evidence (from invertebrate animals to humans), was described. The future applicability that these molecules have due to their biological potential as functional ingredients makes them an important field of research, which could help the world population avoid suffering from several diseases, such as diabetes.

Separation and identification of ACE inhibitory peptides from defatted walnut meal

The peptide obtained from walnut protein enzymatic hydrolysate had high ACE inhibitory activity. Through centrifugation, ultrafiltration, gel chromatography and high performance liquid chromatography (HPLC), the walnut oligo-peptide, which was denoted as P4-c with high ACE inhibitory activity was obtained. Three novel ACE inhibitory peptides, GVVPHN, EHSLDPLK and KTLLNFGPN, were identified from P4-c by high-resolution ion mobility mass spectrometry (IM-MS). The three novel ACE inhibitory peptides possessed good ACE inhibitory activity and the fraction GVVPHN had high ACE inhibitory activity with 27.3 µmol L−1 of IC50. The molar percentage of hydrophobic amino acids in the peptide GVVPHN was 50% while the hydrophobic amino acid contents of EHSLDPLK and KTLLNFGPN were 37.5% and 44.4%, respectively, which indicates ACE inhibitory activities were hydrophobicity of amino acid-dependent.

Soybean Protein Extraction by Alcalase and Flavourzyme, Combining Thermal Pretreatment for Enteral Feeding Product

Soybean is one of the essential ingredients when formulating a tube feeding formula. In this study, we initially focused on determining which enzyme is suitable for hydrolyzing soy and comparing the soy protein enzymatic hydrolysis of three different enzymes at the same enzyme content: Flavourzyme, Protamex, and Alcalase. The result showed that Flavourzyme attained the highest soluble protein recovery efficiency (SPRE). Secondly, the study determined the effect of thermal treatment conditions such as thermal treatment duration, and then it showed that when combining the thermal treatment and enzymatic hydrolysis, the yield reached (61.44 ± 0.22)%, which was much higher than only using enzymatic hydrolysis (52.57 ± 0.27)%. Next, optimizing the enzymatic hydrolysis (combining thermal treatment) using Flavourzyme and Alcalase, Flavourzyme achieved (62.47 ± 0.12)%, while Alcalase attained (41.32 ± 0.13)%. The soy hydrolyzate using Flavourzyme achieved an average molecular size of 3.19 kDa at the following optimizing conditions: enzyme concentration, 16.09 U·g−1; pH, 7.02; temperature, 45.8 °C; and beans/water ratio, 1:3. In contrast, when using Alcalase, the soy hydrolyzate achieved an average molecular size of 1.52 kDa at the following optimizing conditions: enzyme concentration, 28.01 U·g−1; pH, 7.2; temperature, 56.5 °C; beans/water ratio, 1:4.6. Soy protein hydrolyzate of suitable viscosity and particle size flow through the inhaler with branched-chain amino acids achieved a BCAA (Branched Amino Acid) ratio of 2:1:1 for Alcalase and 4:1:1 for Flavourzyme. Soybean hydrolyzate using both enzymes attained a high SPRE and was suitable for the digestive ability of patients recovering from surgery. Soy protein is divided into amino acids, di- and tri-amino acids, and peptides to create a soluble protein source that helps feed patients with a sonde tube easily. In addition, the molecular weight of peptides will reduce viscosity significantly when passing through a sonde tube, preventing tube congestion.

Current knowledge on the extraction, purification, identification, and validation of bioactive peptides from seaweed.

Seaweed (macroalgae) is considered as a sustainable bioresource rich in high-quality nutrients such as protein. Seaweed protein can be used as an alternative to other protein sources. Furthermore, these proteins are natural reservoirs of bioactive peptides (BAPs) associated with various health benefits such as antioxidant, antihypertensive, and antidiabetic activities. However, seaweed-derived BAPs remain underexploited due to challenges that arise during protein extraction from algal biomass. Coupled with this, limited proteomic information exists regarding certain seaweed species. This review highlights the current state of the art of seaweed protein extraction techniques, e.g., liquid, ultrasound, microwave, pulsed electric field, and high hydrostatic pressure assisted extraction. The review also focuses on the enzymatic hydrolysis of seaweed proteins and characterization of the resultant hydrolysates/peptides using electrophoretic and chromatographic techniques. This includes reference to methods employed for separation, fractionation, and purification of seaweed BAPs, as well as the methodologies used for identification, e.g., analysis by mass spectrometry. Furthermore, a bioinformatics or in silico approach to aid discovery of seaweed BAPs is discussed herein. Based on the information available to date, it is suggested that further research is required in this area for the development of seaweed BAPs for nutraceutical applications.

Design and Characterization of a Novel Fermented Beverage from Lentil Grains.

The experimental activities carried out in this study aimed at designing a lentil-based beverage rich in soluble and digestible proteins. In order to extract soluble proteins, lentil grains were soaked in water overnight, blended, treated with proteolytic enzymes and fermented with Lactobacillus strains. Protein enzymatic hydrolysis, carried out with four commercial food grade enzyme preparations, showed that bromelin, at the enzyme to substrate ratio of 10%, was the best solution to produce this novel beverage. Even though the seven Lactobacillus strains were all able to ferment aqueous extract within 24 h, L. acidophilus ATCC 4356, L. fermentum DSM 20052 and L. paracasei subsp. paracasei DSM 20312 showed the highest growth rate and the lowest pH values. In fermented lentil-based beverages, the antinutritional factor phytic acid decreased up to 30%, similarly, the highest reduction in raffinose oligosaccharides content reached about 12% the initial concentration. It is worthy of note that the viable density of all strains remained higher than 7 log cfu/mL after 28 days of cold storage. The results here reported show for the first time the possibility to obtain a probiotic lentil-based beverage rich in soluble proteins, peptides and amino acids with low content in main antinutritional factors.

The Effect of Secondary Structures in Peptides and Proteins on Their Chromatographic Separation

The effect of residual secondary structures in peptides and proteins on their separation is considered within the framework of the lattice model of adsorption and chromatography of macromolecules. It is shown that, if the model takes into account secondary structures, such as helices, folds, or crosslinks, the retention volume may change considerably. At the same time, for short peptides with the number of amino-acid units on the order of 20, which result from the enzymatic hydrolysis of proteins, the effect of secondary structures, for example, residual S–S crosslinks, on separation in the model chromatographic experiment is insignificant. For such peptides the main effect on seраration is exerted by their amino-acid composition, and the values of retention volume may be adequately predicted both under the linear chain approximation and in terms of the adsorption additivity model.

Enzymatic hydrolysis of proteins from snakehead-fish (Channa striata)

The purpose of this research is to study the characteristics and bioactive components of the production of snakehead fish (Channa striata) protein hydrolysates through enzymatic methods. The enzymes used in this study were the papain enzyme and without the enzyme as a comparison. Substrate used is fresh snakehead fish (Channa striata) obtained from fish reservoirs. Analysis carried out in the form of total degrees of hydrolysis and nitrogen content in protein. The results showed that the use of the papain enzyme was excellent in producing snakehead fish (Channa striata) protein hydrolyzate. The papain enzyme helps break down fish protein into peptides or amino acids.

PURIFICATION AND CHARACTERISATION OF ANGIOTENSIN I CONVERTING ENZYME (ACE) INHIBITORY PEPTIDE FROM BLOOD COCKLE (Anadara granosa) MEAT HYDROLYSATE

Blood cockle (Anadara granosa) is the most abundant and available bivalves in Malaysia. Blood cockles meat has high protein content and has potential to generate bioactive peptides. To date, no study has been reported on purification and identification of angiotensin I converting enzyme (ACE) inhibitory peptides from blood cockle meat. Thus, the objectives of this study were to purify and characterize ACE inhibitory peptide from blood cockle meat hydrolysate. ACE inhibitory peptides from blood cockle meat hydrolysate (CMH) were prepared by enzymatic protein hydrolysis using Protamex®. Crude CMH was characterized for its stability against gastrointestinal proteases, at varying pH (2–11) and temperature (4–90°C). Next, crude CMH was purified by ultrafiltration, ion exchange chromatography and reverse-phase chromatography and its amino acid sequence was identified. It was found that crude CMH was highly stable at low pH and temperature, and was resistant to gastrointestinal proteases (pepsin and trypsin). A three-step purification increased the inhibitory activity of CMH, reducing its IC50 from 0.35 mg/ml to 0.0094 mg/ml. The amino acid sequence of the purified peptide was determined as VNDLLSGSFKHFLY, with a molecular weight of 1621.88 Da. This study suggested the potential of ACE inhibitory peptide derived from cockle meat as a nutraceutical ingredient in functional food

Effects of ultrasonic, microwave, and combined ultrasonic-microwave pretreatments on the enzymatic hydrolysis process and protein hydrolysate properties obtained from Chinese sturgeon (Acipenser sinensis).

Degree of hydrolysis (DH), yield, amino acid profile, protein solubility, and antioxidant activity of Chinese sturgeon protein hydrolysates, as influenced by thermal pretreatment, ultrasonic (US), microwave (MW), and combined US-microwave pretreatments were investigated. Initially, the samples were subjected to thermal pretreatments in order to measure their effect on DH, which increased at 55°C. The DH recorded 7.63, 5.55, and 6.02% for US, MW, and combined US-MW pretreatment (US+MW), respectively, at the optimal time (8min). The enzymatic hydrolysis (EN) of pretreated samples increased the DH to 19.41, 14.18, and 16.91% for US+EN, MW+EN, and US+MW+EN, respectively. The US+EN treatment was most effective for obtaining higher DH and yield, which were 19.41% and 18.62%, respectively. The use of US+EN also resulted in an increase in the percentage of molecular weights (≤1,000Da), amino acid content and protein solubility, which reached 89.24, 80.08, and 98.58%, respectively. While, US+MW+EN pretreatment has achieved the highest antioxidant activities by IC50 of 1,1-diphenyl-2-picrylhydrazyl and 2,2-Azinobis (3-ehtylbenzothiazoli- 6-sulfnic acid), which were 3.01 and 1.85mg/ml, respectively, in addition to the reducing power assay, which was 0.528 at a protein concentration of 5mg/ml. Therefore, US and combined US-MW techniques can play a promising role in the production of protein hydrolysates and the improvement of their antioxidant properties. PRACTICAL APPLICATIONS: Nowadays, interest in Chinese sturgeon production has increased as a promising source of protein and antioxidant peptides. The optimal thermal pretreatment can be used to enhance the degree of hydrolysis. The results indicated that the use of ultrasound as a pretreatment enhanced the degree of hydrolysis, which could be useful in the preparation of protein hydrolysate with higher yields. The use of combined US-MW significantly improved the antioxidant properties of the protein hydrolysate. The combined US-MW technique is a novel method for obtaining valuable peptides and protein hydrolysates that can be applied as antioxidant constituents in the food products.

Current genetic engineering strategies for the production of antihypertensive ACEI peptides.

Hypertension is a major and highly prevalent risk factor for various diseases. Among the most frequently prescribed antihypertensive first-line drugs are synthetic angiotensin I-converting enzyme inhibitors (ACEI). However, since their use in hypertension therapy has been linked to various side effects, interest in the application of food-derived ACEI peptides (ACEIp) as antihypertensive agents is rapidly growing. Although promising, the industrial production of ACEIp through conventional methods such as chemical synthesis or enzymatic hydrolysis of food proteins has beenproven troublesome. We here provide an overview ofcurrent antihypertensive therapeutics, focusing on ACEI, and illustrate how biotechnology and bioengineering can overcome the limitations ofACEIp large-scale production. Latest advances in ACEIp research and current genetic engineering-based strategies for heterologous production of ACEIp (and precursors) are also presented. Cloning approaches include tandem repeats of single ACEIp, ACEIp fusion to proteins/polypeptides, joining multivariate ACEIp into bioactive polypeptides, and producing ACEIp-containing modified plant storage proteins. Although bacteria have been privileged ACEIp heterologous hosts, particularly when testing for new genetic engineering strategies, plants and microalgae-based platforms are now emerging. Besides being generally safer, cost-effective and scalable, these "pharming" platforms can perform therelevant posttranslational modifications and produce (and eventually deliver) biologically active protein/peptide-based antihypertensive medicines.